Records of Montes Service’s fuel oil consumption for the last six-month period show that Montes paid $1.085 per litre for the first 1100 litres, $1.093 per litre for the next 1600 litres, and $1.121 per litre for the last delivery of 1400 litres. Determine the average cost of fuel oil per litre for the six-month period.

Solve each of the following problems involving an arithmetic average.